The coming years will see the market for electronic devices and logic boards grow by additional leaps and bounds. But as electronics and semiconductors infiltrate new industries and products, designers and manufacturers are always on the hunt for better and smarter ways to manufacture these vital components.
Silicon carbide semiconductors are one such development. But to what do we owe their growth in popularity? And which devices have made the switch — or plan to in the near future?
Silicon Carbide Answers Common Silicon’s Shortcomings
Silicon carbide (SiC) power semiconductors stand out from common silicon semiconductors (also called “IGBTs”) for several reasons, most of which have to do with the inherent limitations of silicon itself. When used in powered electronic devices and power systems, silicon displays:
- Limited thermal conductivity
- Difficulty switching frequencies in some applications
- Low band gap energy
- Higher power loss
With these limitations in mind, let’s take a closer look at the advantages introduced by silicon carbide power semiconductors (also called “SiC MOSFETs”).
Silicon Carbide Withstands Higher Voltages
Power semiconductors made from silicon carbide are capable of withstanding voltages up to 10 times higher than ordinary silicon. This, in turn, has a number of implications for system complexity and cost.
Because SiC tolerates higher voltages, power systems built on silicon carbide semiconductors require fewer switches in series. This means simpler and more reliable system layouts as well as lower costs for manufacturers thanks to a reduced number of components.
Silicon Carbide Operates at Higher Temperatures
The proliferation of electronic products throughout the world means many types of devices that must operate in variable or harsh conditions, such as higher temperatures. Silicon carbide shines here as well.
Common silicon IGBTs demonstrate a relatively poor degree of thermal conductivity. Power semiconductors made from silicon are generally rated to operate as expected in temperatures no greater than 150°C. In comparison, SiC semiconductors can maintain functionality and integrity at temperatures of 200°C or more, thanks to a thermal conductivity that improves upon common silicon by a factor of three. It should be noted, however, that most commercial-level semiconductors of this type still receive a recommended temperature rating of 175°C or thereabouts.
As with the higher voltage ratings mentioned previously, higher temperature ratings also play their part in reducing system design complexity, increasing reliability and lowering costs for manufacturers. Thanks to SiC semiconductors, system designers can use smaller and fewer capacitors and storage inductors, which brings down the total cost of the electrical system.
In Which Industries and Products Are SiC Semiconductors Most Useful?
Increasingly, the automotive market is “ground zero” for demand and innovation in silicon carbide semiconductors. Between 2016 and 2017, the market for SiC power devices jumped from $248 million to $302 million. Companies like Tesla, Toyota and others, who lead the pack in terms of electric vehicle innovation, are big reasons for this higher demand.
Electric and driverless vehicles with onboard charging units and traction inverters are prime candidates for SiC semiconductors. But these are far from the only high-voltage applications to which SiC MOSFETs are well suited. Here are some of the other industries and products where silicon carbide is finding a home in power system design:
- Military systems
- Sensor systems
- Solar power inverters and other power supplies
- Wind turbines
SiC is part of a hierarchy of semiconductor materials that meets a range of power needs. Common silicon has historically been the material of choice for power requirements of five volts or below. Then came gallium-nitride (GaN), which performs well in systems ranging up to 1,000 volts. SiC has emerged as the semiconductor material of choice for system designs that must accommodate 1,000 volts or more. SiC and GaN were developed and came into vogue more-or-less in tandem, but SiC has “caught on” in the market in a way GaN has not.
Here’s how the band gap performances of these three major semi technologies compare:
- Common silicon band gap: 1.1 eV
- SiC band gap: 3.3 eV
- GaN band gap: 3.4 eV
Remember that a wider band gap results in a power system that can run at higher voltages. This makes SiC and GaN complementary and somewhat similar products.
This hierarchy of semiconductor materials results in various levels of energy loss as well. According to experts, using SiC in electric motors can reduce power loss by an impressive 80 percent. In turn, this means designers can incorporate smaller batteries, but enjoy lower power requirements and costs, without sacrificing product performance.
Is There a Downside to Silicon Carbide Semiconductors?
For the time being, the cost is one of the few notable downsides in bringing SiC semi technology into a wider variety of electrical and power products. A SiC semiconductor could cost five times as much as a common silicon IGBT. Nevertheless, the somewhat higher costs are a tradeoff worth making for many product and power system designers. Thanks to improved performance and lower costs elsewhere due to simpler and more reliable designs, companies everywhere are embracing SiC semiconductors in a big way as we explore next-generation technologies.